Traditionally, an aerial lift comprises a motorized chassis, wheels, a turret pivoting at 360° on the chassis, a telescoping arm articulated on the turret, and a moving platform arranged at the end of the telescoping arm. Such a lift must be able to travel narrow passages easily and be transported without requiring heavy transport. The length and width of the lift must therefore be reduced, while keeping a high lifting performance.
The lift must also have significant stability, because there is a risk of tilting during its use, for example when the telescoping arm is inclined excessively. Such tilting must be avoided, in particular when an operator is on the moving platform located at height. In practice, the stability increases with the separation between the ground bearing points of the lift, i.e., the wheels equipping the chassis. Separating the wheels makes it possible to improve stability during use, but increases the bulk of the lift at the same time.
Thus, depending on the usage conditions, a compromise is sought between two critical and contradictory parameters.
In a known manner, an aerial lift may be equipped with extendable and retractable axles. For example, U.S. Pat. No. 6,119,882 describes a vehicle, of the aerial lift type, comprising two axles mounted on a chassis. Each axle includes two symmetrical support arms mounted across from each other in a central box. Each support arm is connected to a wheel of the vehicle and is moved by a hydraulic cylinder to allow its movement outside the central box. When the axles are retracted, in particular during movement of the lift, its widthwise bulk is reduced. When the axles are extended, in particular in the working position of the lift, its stability is improved. The extension travel of each support arm of such axles is nevertheless limited to a maximum of the half-width of the central box.
To resolve this drawback, one solution known from the prior art consists of mounting, within the central box, one of the support arms sliding inside the other support arm. This arrangement makes it possible to obtain telescoping support arms and thus to increase their extension travel. This increased extension travel of the support arms is, however, limited by the fact that both support arms must remain constantly bearing on each other, to respect the structural integrity constraints of the lift and the distribution of the forces exerted on the axle. This is not satisfactory, in particular in terms of limitation of the stability of the lift following limitation of the extension travel of the support arms.